The present invention relates to the detection of skin abnormalities and, more particularly, to the detection of cancerous or precancerous skin tissue using autofluorescence.
Whether due to increased awareness or a variety of environmental factors, the incidence of detected cases of skin cancer is increasing. Because most skin cancers are curable if treated early, there is an increased emphasis on the detection of malignant or premalignant skin tissue. The majority of skin cancers are detected based on a visual observation of a patient""s skin under white light by a trained dermatologist. However, the success of such a method relies heavily on the ability of the physician to distinguish healthy skin from a potentially malignant lesion.
One technique that can aid a physician in the detection of cancerous or pre-cancerous lesions is based on the difference in autofluorescence light produced by healthy and non-healthy tissue. All tissue will fluoresce or produce light within a well-defined range of wavelengths when excited. It is known that the autofluorescence light produced by healthy tissue has a spectral profile that differs from that produced by non-healthy tissue. A number of research groups have exploited this difference in the spectral profile by recording the wavelength spectrum of a single point. Although this provides interesting data, it is clinically difficult to use.
One system for detecting cancerous tissue based on differences in autofluorescence light is described in U.S. Pat. No. 5,507,287, which is assigned to the Xillix Technologies Corporation of Richmond, B.C., Canada, the assignee of the present invention. However, this and similar systems generally require a computer monitor and image processing equipment in order to produce images of suspect tissue and are not portable enough to be used outside a hospital. In addition, these systems are relatively expensive and require significant amounts of energy to operate.
A lightweight, portable system for the detection of autofluorescence light of the skin is described in PCT application PCT/CA97/00919, entitled xe2x80x9cFluorescence Scope System for Dermatologic Diagnosis.xe2x80x9d However, depending on the embodiment, this device either lacks sensitivity due to the lack of light amplification, or is difficult to use due to the requirement for the user to mentally combine images of different colors presented to each eye.
To increase the ability of medical personnel to perform screening tests on greater numbers of patients, there is a need for a low-cost, lightweight, portable cancer detection system that can aid physicians in the detection of potentially malignant lesions based on differences in the autofluorescence light produced by healthy and suspect tissue.
The present invention is a lightweight, hand-held skin abnormality detection imaging system including a source of excitation light which causes tissue under examination to produce autofluorescence light. The autofluorescence light generated from the tissue under examination along with reference light is directed to a pair of optical channels that produce an image of the tissue under examination. An optical combiner, which preferably comprises a dichroic mirror, superimposes the images of the tissue to be viewed by a user.
In one embodiment of the invention, the autofluorescence light received in one channel has a wavelength selected such that the autofluorescence intensity for healthy tissue differs from the autofluorescence intensity produced for diseased or suspect tissue. The reference light comprises autofluorescence light, wherein the autofluorescence intensity for diseased tissue is substantially similar to the autofluorescence intensity for healthy tissue. In another embodiment of the invention, the reference light comprises reflected excitation light. In yet another embodiment of the invention, the reference light comprises light having wavelengths that differ from the wavelengths of the excitation light.
The combined superimposed output images may be viewed by a user or may be captured by an analog or digital camera. For viewing by a user, these embodiments can all be implemented with monocular or binocular viewing.